US2605256A - Use of mercaptans in copolymerization of vinyl sulfides with acrylonitrile - Google Patents

Description

Patented July 29, 1952 UNITED STATES PATENT oFF cs 2,605,256 i v 'USE OF MERCAPTANS IN COPOLYMERIZA-Y- J TION or VINYL SULFIDES WITH ACRYLO-' NITRILE -Wend"elI It. Conard, Kent, and Chris'EI'Best; Franklin- Townshi Ohio, assignors to-gTh'e Firestone Tire & Rubber Company, -;Akr.on,

Serial No. 96 ,833

10 Claims. (01. 260-7937) l This invention relates to modification of the copolymerization of a vinylsulfide and acrylonitrile, methacrylonitrile or ethacrylonitrile, using a mercaptan modifier. v

The mercaptan' modifier is fromthe class consisting-of alkyl, aryl, furyl-,and-furf-'uryl mercaptans. The alkylsubstituents may-besubstituted or cyclic. The class of modifiers may, therefore, more precisely be defined as consisting of the alkyl, aryl, fury-l, and'f'urfuryl mercaptans including hydrocarbon-substituted alkyl and cycloalkyl mercaptans, said alkyl, hydrocarbonsubstituted alkyl' and cycloalkyl each contain- 6 ing one to twelve carbon atoms.

It includes, for example, methyl mer'capt'an, ethyl mercaptan, the various propyl, butyl, amyl, 'liexyl, heptyl, octyl, nonyl, decyl. undecyland dodecyl mercaptans (including isopropyl' and n-propyl', n-butyl, sec.-butyl, and tert.-buty-l, etc.)'-, cyclohexyl, cyclopentyl mercaptans, etc., benzyl mercaptan, etc., furyl mercaptan, furfuryl m'ercaptan, thiophenol, thiotoluol, thio-alpha-naphthol, thiobeta-naphthol, the thiocresols, the-thioxylenols, etc. It includes mixed mercaptans, e. g., those obtained as a by-productof petroleum refining and those obtained from a mixture of by-product hydrocarbons derivedfrom petroleum refining,

etc. 1

Modifiers of this class: cause: thev production of copolymer resins which are more plastic and therefore more easily worked than the-unmodified resins. Likewise, the modified copolymer-s'swell or dissolve more readily in solvents than do the unmodified resins. Although the invention is applicable to copolymerization of any vinyl sulfide with any acrylonitrile derivative, its preferred application is in the modification of those copolymers which are difficultly workable or diflicultly swellable or soluble in solvents, and as set forth herein is limited to modification of copolymers obtainable from (1) vinyl sulfides containing a benzyl, phenyl, or alkyl group of one to four carbon atoms and (2) acrylonitrile, methacrylonitrile, or ethacrylonitrile.

The mercaptans improve the plasticity and solubility of the copolymers; andmay affect their toughness. The amount or modifier employed determines the extent of the modification. Equal molecular proportions of the different mercaptans modify to substantially the same extent. The use of a large amount of modifier may embrittle the copolymer.

Although the invention will be described more particularly with respect to the modification of emulsion copolymerization, the mercaptans also v II 2 i modify copolymerization'by other processes such as mass copolymerization, solution copolymerization, etc. The process of copolymerization may vary widely. The temperature range may vary and although temperatures of 10 to C. are preferred, the process is not limited thereto. Different catalysts, etc., may be employed. All of the monomers may be present at the start of the copolymerization or may be added in increments during the reaction. The concentration of the mercaptan may be varied from, for ex ample, 0.2 to 5.0 parts of mercaptan per parts of total monomer used, and has'general application. to the modification ofcopolym'erization of I the said monomers regardless of the particular method of copolymerization.

In. carrying out the; reaction air. is excluded by replacement with nitrogen, because oxygen inhibits the polymerization. The ratio of the vinyl sulfide: to the. acrylonitrile, etc. maybe varied.. If more thanon'e molecular weight of sulfide is used for'each'molecular weight of acrylonitrile, etc., the excess sulfide does not enter into the reaction. The higher the percentage of acrylonitrile, etc. entering into the reaction, the more diificult the copolymer is to mold or dissolve, etc. Generally an excess of acrylonitrile, etc. willbe employed in the reaction mixture, although all of the excess will not necessarily enter into the copolymer. From one to five molecular equivalents of the acrylonitrile, etc. may be used in the reaction for each' molecular equivalent of sulfide. A preferred copolymer is constituted of 1.0 to 1.25 molecular equivalents of the acrylonitrile, etc. to eachmolecular equivalent of the vinyl sulfide. v V V The higher the molecular. weight of the sulgreatest value inthe. modification of. copolymers obtained from the lower molecular'weight sulfides and herein. is limited to modification of the copolymerization. of. acrylonitrile, methacrylonitrile or ethacrylonitrile with the benzylj and phenyl vinyl sulfides and those alkyl vinyl sulfides which contain one to four carbon atoms in the alkyl group; These alkyl vinyl sulfides include those containing a methyl, ethyl, n-propyl, isopropyl,

n-butyl, see.-butyl or tert.-buty1 group.

The plasticities specified below were determined by pressing 050 gram samples of the resins between polished plates in a Carver laboratory press at 2000 pounds per square, inch at C. The

area of the resulting, fused disc measured in s uare millimeters is the plasticity.

3 EXAMPLE 1 To illustrate the efiect of the modifier in the vinyl sulfide reaction, the following formula was.

sulfates) grams 10.0

Sodium bicarbonate do 12.8 The sodium bicarbonate is present as buffer; J

Carrying out the reaction in a two-liter, three- 1.5

v The charge was agitated at 40 C. for two hours.

neck, round-bottom flask equipped with reflux condenser, thermometer and stirrer, and im-.

mersed in a bath to obtain controlled temperature, 1

with passage of nitrogen through the flask throughout the reaction, the results obtained, using difierent temperatures and different amounts of mixed-amyl mercaptan as additional modifier, are illustrated in the following table:

The table indicates that the use of increasing amounts of mercaptan gives a more plastic product.

The following table shows the difference in solubility in various solvents between unmodified copolymer of methyl vinyl sulfide and acrylonitrile prepared as above, and modified copolymer so prepared in the production of which there. is used at least 0.8 part by weight of the 'amyl mercaptan per 100 parts of total monomer:

Solubility table Solvent: Unmodified Resin Modified Resin Nitromethane. Swells strongly Soluble (warm). Nitropropane do. Do.. I

Cyclohexanone Ethylene Chlorid Ethylene Ohlorhydrin do 0. Epichlorhydrin Soluble (warm) do Dimethyl Formamide. swells very strongly. Soluble (cold).

we s

Mesityl Oxide S Soluble (warm).

moderate stirring. High speed agitation produced apparent solution of the unmodified resin in nitromethane, nitropropane, cyclohexanone, and ethylene chloride, but these were merely dispersions-which gelled on standing. The solution of the modified copolymer at 60 C. in nitromethane was clear and a true solution, visibly distinguishable from the mentioned dispersions which were merely translucent and not clean Any copolymer of methyl vinyl sulfide and acrylonitrile,

constituted of 1 to 1.25 molecular equivalents of the latter for each molecular equivalent of the 'former, which is sufficiently soluble in nitromethane at 60 C. to produce a ten per cent (by weight) solution, is new.

Mixtures of some solvents have more power than the individual solvents. For instance, nitromethane' and ethylene chloride is more powerful than either alone. A mixture of nitromethane i The above tests were made with no more-than and ethylene chlorhydrin is the best mixture yet found.

EXANIPLEI 2 A copolymer :lwas preparedfrom the following charge 7 Methyl vinyl sulfide grams 54 Acrylonitrile r do 46 Water i cc 400 Ammonium persulfate grams 3.2 Sodium bicarbonate do 6.4 ,.Aquarex D do 5 Mixed-amyl merc'aptan cc 0.8

The resulting copolymer was found to be at least 10 per cent soluble in hot nitromethane.

. Also the modified copolymer was soluble at room temperature in a mixture of equal volumes of nitromethane and ethylene chlorhydrin to give a clear, viscous (500-2000 cps.) solutionata concentration of 10 percent. Filmscastjrom this solution, when dry, were coherent and strong and of good clarity and appearance;

Copolymer prepared as above but" omitting the mercaptan formed a gel in hot nitromethane ,and was not soluble to ;the, extent ofgilQper cent. This unmodified copolymer swelledstrongly but did not dissolve in a lzl mixture of nitromethane and ethylene chlorhydrin, even on heating; Such a gel of 10 per cent concentratiomcould be broken to a pseudo solutionjby violent agitation such as -.is produced by a Warin Blendor, but this was opalescent and opaque andrather thin, and so unstable that on standing -it tended to revert to a gel, Films produced fromit were irregular and developed norycoherent-portions .on drying; whichwere not apparent in films from solutions of;the modifi ed copolymer which it'is believed were true solutions whereas the unmodifed copolymersv produced merely V dispersions of gel particles} 7 v The charge of Example .1 was used in this test, but various mercaptans were used as modifiers.

The mercaptans are listed in the followingtable,

together with the amounts of each, and theplasticities of the-products; All plasticities are higher than that for unmodified resin., 1;;

IElxamplc Mercaptan- Amount Yield Plasticity.

. "Percent.- V Amyl 0.5 88. 1. 658 t-0cty1 1L6 90.4 1, 538 Thiophenol- 0.188 88.4 1,538 t-D0decyl l; 6 88. 8 1, 734 t-Butylufl; I 0; 72; 86. 8 l, 734

' EXAMPLE 4' Thirteen and five-tenths grams methyl vinyl sulfideand. 11.5grams acrylonitrile were-reacted in cc. water using 0.8 gram ammonium persulfate as catalyst, 0.4 gram Aquarex D as emulsifying agent and difierent modifier compositions i ketone.

The table shows the low plasticity and insolubility in methyl ethyl ketone of the copolymer obtained without mercaptan, and the effect of increasin amounts of amyl mercaptan.

What we claim is:

1. The process which comprises copolymerizing one molecular equivalent of an alkyl vinyl sulfide having one to four carbon atoms in the alkyl group, with one to five molecular equivalents of a monomer of the class consisting of acrylonitrile. methacrylonitrile and ethacrylonitrile, in the presence of 0.2 to 5.0 parts per hundred parts of total monomer, of a mercaptan of the class consisting of alkyl, cycloalkyl, aryl, fury], and furfuryl mercaptans, said alkyl and cycloalkyl each containing one to twelve carbon atoms.

2. The process of claim 1 in which there is produced a copolymer constituted of 1 to 1.25 molecular equivalents of the second-mentioned monomer for each molecular equivalent of vinyl sulfide.

3. The process of claim 1, in which the copolymerization is modified with a non-cyclic alkyl mercaptan containing one to twelve carbon atoms.

4. The process of claim 1 in which the mercaptan used is amyl mercaptan. 5. The process of claim 1 in which an alkyl mercaptan is used, the copolymerization is effected in an aqueous emulsion, and the copolymer is formed from 1 to 1.25 molecular equivalents of the second-mentioned monomer for each molecular equivalent of vinyl sulfide, the temperature being to 60 C.

6. The process of claim 1 in which amyl mercaptan is used, the copolymerization is effected in an aqueous emulsion and the copolymer is formed from 1 to 1.25 molecular equivalents of the second-mentioned monomer for each molecular equivalent of vinyl sulfide, the temperature being 10 to C.

7. The process of claim 1 in which an alkyl mercaptan is used, the copolymerization is effected at 10 to 60 C. in an aqueous emulsion of acrylonitrile and methyl vinyl sulfide, and a copolymer is formed from 1 to 1.25 molecular equivalents of acrylonitrile for each molecular equivalent of methyl vinyl sulfide.

8. The process of claim 1 in which amyl mercaptan is used, the copolymerization is effected at 10 to 60 C. in an aqueous emulsion of acrylonitrile and methyl vinyl sulfide, and a copolymer is formed from 1 to 1.25 molecular equivalents of acrylonitrile for each molecular equivalent of methyl vinyl sulfide.

9. A copolymer constituted of copolymerized acrylonitrile and methyl vinyl sulfide in the ratio of l to 1.25 molecular equivalents of the former for each molecular equivalent of the latter, which copolymer is soluble in nitromethane at 60 C. to produce a ten per cent solution.

10. Easily worked and readily soluble copolymer constituted of a monomer of the class consisting of acrylonitrile, methacrylonitrile and ethacrylonitrile, and an alkyl vinyl sulfide in which the alkyl group contains one to four carbon atoms, in the ratio of l to 1.25 molecular equivalents of the former for each molecular equivalent of the latter.

WENDELL R. CONARD. CHRIS E. BEST.

REFERENCES CITED lihe following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,388,160 Krase Oct. 30, 1945 2,395,327 Hanford Feb. 19', 1946 2,434,054 Roedel Jan. 6, 1948 FOREIGN PATENTS Number Country Date 662,156. Germany July 7, 1938 586,881 Great Britain Apr. 3, 1947

Claims (1)

1. THE PROCESS WHICH COMPRISES COPOLYMERIZING ONE MOLECULAR EQUIVALENT OF AN ALKYL VINYL SULFIDE HAVING ONE TO FOUR CARBON ATOMS IN THE ALKYL GROUP, WITH ONE TO FIVE MOLECULE EQUIVALENTS OF A MONOMER OF THE CLASS CONSISTING OF ACRYLONITRILE, METHACRYLONITRILE AND ETHACRYLONITRILE, IN THE PRESENCE OF 0.2 TO 5.0 PARTS PER HUNDREDED PARTS OF TOTAL MONOMER, OF A MERCAPTAN OF THE CLASS CONSISTING OF ALKYL, CYCLOALKYL, ARYL, FURYL, AND FURFURYL MERCAPTANS, SAID ALKYL AND CYCLOALKYL EACH CONTAINING ONE TO TWELVE CARBON ATOMS.